Control system for railway classification yard



May 24, 1966 J. H, AUER, .JR

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD 9 Sheets-Sheet 1 Filed April l5, 1956 HIS ATTORNEY May 24, 1966 J. H. AUER, .JR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD 9 Sheets-Sheet 2 Filed April l5, 1956 bn.. WJ IU A H. IU.

Qmmaw HIS ATTORNEY III Kwam/imm OPOmFmQ aDOm@ NZ May 24, 1966 .1. 1-1. AUER, JR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April l5, 1956 9 Sheets-Sheet 5 SPEED STORAGE RELAYS ..EJ E

HUMP LEAV|NG SPEED STORAGE Jl AND TRANSFER CIRCU1TS19 SIP S2P SBP S4P S5P E CUT LENGTH /28 DETECTOR l 1 1 1 1 1 2TPS-A 1 1 lREFERENCE ENTER1NG :1/ QZTPS I SREED C1RCU1TS 27 24S 2471 2481 491 5d D r l -f- I I FEEL 1 IN V EN TOR.

JHAUER JR.

GROU P MAN UAL MODI FYING CONTROLSS May 24, 1955 J. H. AUER, .IR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April l5, 1956 9 Sheets-Sheet 4:

FIG. 3B. I NOI. CROUP NO.2.GROUP RETARDER RETARDER wEIOHING RAIL TRANSMITTING AND TRANSMITTER 42 TRANSMITTER 48 RECEIVING ANTENNAS RECEIVER RECENER |95 I NOIDISCRIMINATOR 5S I CATHODE I/SS PULSE L97 /200 SPEED RELAY /20I I *FOLLOWER FORMING AMPLIFIER CONTROL SI CIRCUITS 205 CIRCUITS I -I-L. I l202 I CHECK RELAY /ISe ANTICIPATION I I- CONTROL w-I -RELAY CONTROL- --I AI I CIRCUIT I CIRCUIT I I 204( I I L EXIT RELAY |99 I I CONTROL --I I I- CIRCUIT I I SEE RELAY SI'l CONTROL VOLTAGE FICAB. RELAY AI CONTROL VOLTAGE IB-P-I |208 /265 S20 I'I z MODIFIER 54 32? T I SOUARING PULSE CLAMPER AMPLIFIER CLAMPER AMPLIFIER GATE CLAMPER 257 CATHOOE OCAMPLIFIER 26S (B+) (B+) IB+I 30| INVENTOR. J.H.AUER JR.

BFM/@722,2

HIS ATTORNEY May 24, 1966 J. H. AUER, JR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April l5, 1956 9 Sheets-Sheet 5 FIG. 5C.

No.2. OISCRIMINATOR 44 I" l CATHODE PULSE SPEED RELAY FORMING AMPLIFIER CONTROL ----.S2 FOI-LOWER CIRCUITS CIRCUIT CHECK RELAY ANTICIPATION I CONTROL RELAY CONTROI- A2 CIRCUIT I CIRCUIT I I ExIT RELAY I CONTROL -1 I CIRCUIT I I I FPO 1ZC'K mi SSI SEE {RELAY S2 CONTROL VOLTAGE PIG.4B. RELAY "A2CONTROL VOLTAGE 1| SISI IVIO-I 2 322 FI SI5 j E 327 ONE-SHOT VOLTAGE MULTI- AMPLIFIER SAMPLING VIBRATOR CIRCUIT 272 275 SIS 274 ELECTRONIC Sw.3O2 523 32? INOISTORAGEI 3,7 CATHODE (B+) 55o 51S FOLLOwER 528 3 I I (5")l 332 I 29 506 ELECTRONIC 05 CATHODE SWITCHES B+) No.2 STORAGE FOI-LOWER INVENToR. J. I-I. AUER JR. (EI-IT 54 BY HIS ATTORNEY May 24, 1966 J. H. AUER, JR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April l5, 1956 9 Sheets-Sheet 6 REELEAVING SPEED CIRCUITS 4o FIGA'B' IGROUP RETARDERSI A NO. I GROUP No.2. GROUP RETARDER RETARDER SIMILAR TO REF.

LEAVING SPEED CIRCUITS FOR NO,I. GROUP RETARDER I RELAY"SI' RELAYAI' RELAY'S2' L ;I'QGAHGTE CONTROL CONTROL L SQIEE CONTROL RELAYS FPO VOLTAGE VOLTAGE RE LAYS VOLLYAZ" FIG 4A SEE FISSE. CONTROL VOLTAGE I-IUMP LEAVING SP/EEO CIRCUITS 25 lLIGHT CAR SEE FIG.3C. MOOIFYING CONTROL I+I wSP FIG. 7

ITI HUMP RETARBER g D 'I 2. Lu

2I5 I 2I4 I E 9 Q In (D x E A *N v v I g x O I Il. TQQ/22o n E E /TRACK I M 2|? i I g I I E, I- A IIE *IML EJ ERI f ES I 2R14? fI I I+)224 HJ I Y cr t I 2II/ 2I5/ GROUP LEAVING SPEED LET) l INVENToR.

| I u J.II.AUER JR.

LwEIGI-IT I RELAYFQ'S' RELAYA BY -STORAGE I5. CONT OL CONTROL RELAYS VOLTAGE VOLTAGE May 24, 1966 J. H. AUER, JR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April l5, 1956 9 ShGetS-Sheet '7 NVENTOR J. HUER JR HIS ATTORNEY BINARY COUNTING CIRCUITS 59 May 24, 1966 J, H, AUER, JR 3,253,141

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April l5, 1956 9 Sheets-Sheet 8 STT- i SPEED CODE STORAGE RELAYS 5| 8 E* INVENToR. N S w J. H. AUER JR 5 BY HIS ATTORNEY May 24, 1966 J. H. AUER, JR

CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD Filed April 1s, 195e 9 Sheets-Sheet 9 United States Patent NTO 3,253,141 CONTROL SYSTEM FOR RAILWAY CLASSIFICATION YARD .lohn ll-I. Auer, Jr., Greece, N.Y., assignor to General Signal Corporation, a corporationof New York Filed Apr. 13, 1956, Ser. No. 578,047 1 Claim. (Cl. 246-182) This invention relates to the automatic control of .the speed of railway cars in a classication yard, and more particularly pertains to a system for controllingthe application and release of braking pressure of trackbrake type car retarders to provide car coupling at suitable speeds.

In a classification yard, a train of railway freight cars is pushed over the crest of a hump, and eachcar is then allowed to roll by gravity down the hump and over a number of route-selecting switches to a particular one of a number of destination tracks. When several successive cars are to go to the same destination track, they are usually kept coupled together and allowed to roll together to their destination track; such a group of cars is called a cut. In this way, the cars of a train are classied according to their intended destinations.

The height of the hump is made to be more thansuicient to enable a car having high rolling resistance, to roll over a route providing maximum resistance to aremote destination in the classification yard and couple onto other cars in that same destination track. Cars having easier rolling characteristics and travelling over a route presenting less resistance must, consequently,-be decelerated so that they too will reach their destination tracks and couple with a speed that is notexcessive. This deceleration is accomplished by providing car retarders along the track rails whose brake shoe beams apply controllable braking pressure tothe rims of the car wheels.

In rolling from the crest of the hump, the cars are switched from the main track to a plurality Ofbranch tracks and then over additional switches to their nal destination track. One or more car retarders are located along the main track, and these are called hump retarders. Additional car retarders are included in some of the branch tracks as well so that the speed of each car or cut can be now accurately controlled for the particular conditions relating to the track it will travel over, and these retarders are called group retarders. Where conditions require it, a series of adjoining retardersrather than one is located along the track rails to provide the required amount of retardation.

In the past it has been the practice to have the braking effect of the various retarders controlled by an operator who observes the speed of each car or cut and then takes into account the cars weight, its rolling characteristics, destination, wind resistance, and other factors to determine how much retardation should be applied. These many independent factors, whose value can for themost part be only roughly estimated by an operator, make it exceedingly difficult to control the retarder precisely. The retarder operators task becomes more dicult when, as often happens, several cars r cuts are passing simultaneously through the yard over diverse routes so that they occupy different retarders at about the same time. In such a system any misjudgment by the retarder operator results in unsatisfactory operation. A car may fail to 3 ,253, l 41 Patented May 24, 1966 reach its intended destination if it has been given too much retardation, or it may enter its destination track at too high aspeed if it has not been given sufficient retardation and it may then cause damage as it couples at high speed with the other cars already in the destination track.

To overcome these difficulties, a system was provided for controlling the retarders automatically with the objective of causing each car or cut to leave the group retarder at a speed that would cause it to couple in its destination track at the desired coupling speed. This prior system is fully disclosed in a prior co-pending application of H. C. Kendall and J. H. Auer, Jr. Ser. No. 513,364 filed ,June 6, 1955, and now abandoned. This system comprises computing means which receives information for each car as to its destination track, weight, and rollability, and from this data determines what the desired releasing speed from the `group retarder should be. Speed measuring apparatus is also provided and is effectivenot only in determining .the rollability factor of each car by measuring `its average acceleration over a test section having known characteristicsbut also to cause the release of the retarders when the car speed has reached a proper value. The important factor of car rollability is measured in this prior system by determining the acceleration each car experiences as it rolls by gravity between the hump and group retarders. Each car is assumed to leave the hump retarder at a predetermined speed so that its speed at the entrance to the group retarderis-then assumed to provide a measure of the cars acceleration since leaving the hump retarder.

Thesystem of the present invention is to be considered as representing an improvement over that disclosed in this prior-mentioned co-pending application Ser. No. 513,364. In this Vpresent system, whose details will presently be fully discussed, it is Vno longer assumed that a release speed of a car from the hump retarder is a constant value. Instead, speedmeasuring apparatus is provided which accurately measuresthe speed of each car at the momentit leaves thehump retarder. This actual speed of leaving the hump retarder is then used to predict the speed of arrival at the group retarder for a car of .known rolling characteristics. Deviations from/this predicted or reference entering speed determine the cars rollability. For each car or cut, a reference leaving speed from the group retarder is selected in accordance with its weight classiiicationand the route it will take after leaving the group retarder. The rollability factor modifies this reference leaving speed to give the actual .group retarder leaving speed.

The present invention is a further improvement over that disclosed in the former system in that it is possible to adjust the group retarder release speed for each car more in accordance with the exact conditions relating to the particular car. lFor example, the modification of reference leaving speed of each car from the group retarder in accordance with car rollability is further aifected by the route it is to take after leaving the group retarder rather than by the rollability factor alone.

,Another advantage provided by the system of this invention is the kabilityfto modify the group retarder release speed according to the distance the car must travel before coupling with other cars in its classiiication track. This can be accomplished automatically by means capable of detecting track fullness or can be accomplished effective on each car.

u manually as is particularly disclosed herein. This function of the system is accomplished by selecting different multiplying factors according to track fullness for a computing device known as a modifier.

The system provides apparatus associated with each car ret-arder that constantly measures the speed of a car in the retarder or immediately in approach of the retarder. This apparatus is of the continuous-wave radar type wherein the frequency shift of ahigh frequency signal reflected from a 4moving car is, according to the Doppler principle, proportional to the cars speed. Speed measuring apparatus is associated with the hump retarder to cause it to release each car at a preselected speed. Additional speed measuring apparatus. associated with the hump retarder is provided to -actually determine what the speed of each car is at the moment it leaves the hump retarder. As each car approaches the group retarder it is to pass through, its speed is again determined by speed measuring apparatus associated )with that particular retarder. The amount by which the speed of the car has increased since leaving the hump retarder provides a measure of its comparative rollability.

The release o-f a retarder results directly from the actuation of an electromagnetic relay operated by a unit called a discriminatorf The Doppler beat frequency signal proportional to car speed is applied to this discriminator, and when this beat frequency signal reaches a certain frequency value, indicating that the car speed has been reduced by the retarder to the desired value, the relay is actuated and the retarder is released. The computation of the desired car speed at which the discriminator causes this relay to be actuated is influenced by Various factors. Thus, the cars weight is a variable factor which is applied as an input to the discriminator and used in determining the release speed. With respect to the group retarders, the particular route a car will take upon leaving the group retarder is obtained from the automatic switching circuits, .and this information is also used as an input factor to determine the release speed from the group retarders. This information as to route is important in determining the release speed from the group retarder because the a-mount of track curvature a car encounters determines to a considerable extent the frictional forces Similarly, the comparative roll- Iability of each car or cutis applied as another input factor from the modifier to aid in determining release speed from the group retarder. In addition, manually operable controls are provided so that an operator can increase ordecrease the release speed by preselected amounts. Thus, all the various factors which affect the speed of the car Iafter leaving the group retarder are taken into account, each with the proper weight given to it, to determine the desired release speed from t-he retarder.

A cut of several cars is not able to roll freely between the hump and group retarders for as long a time as a single car. A measurement of the velocity of such a cut at the entrance to the group retarder does not, therefore, provide an accurate measure as to the rollability of such a cut. A very long cut, moreover, may not roll freely at any time over the test section since the last car may still be in the hump retarder by the time the rst car of the cut is about to enter the group retarder. In the system of this invention, such long cuts are detected as such and the computation of the desired release spe-ed from the group retarder is affected accordingly.

It is, accordingly, an object of this invention to determine the rollability of each car or cut by measuring its velocity at two fixed locations ahead of -the group retarder. The difference in the two velocities gives the cars average acceleration between the locations, thereby making it possible to evaluate its rolling ability.

Another object of this invention is to provide for a variable release speed from the group retarder in accordance with the particular conditions a car is likely to cncounter over the route it must take to its preselected classification track.

Another object of this invention is to provide for a variable release speed in the group retarder in accordance with the fullness of the particular classification track the car is intended to Sgo to.

Other objects, purposes, and characteristic features of this invention will in part be obvious from the accompanying drawings and in part pointed out as the description of the invention progresses.

lIn describing this invention in detail, reference will be made to the accompanying tdrawings in which like ref-erence characters designate corresponding parts in the different views, and in which:

FIG. 1 diagrammatically illustrates a portion of the track layout of a typical car classification yard;

FIGS. 2A a-nd 2B are a block diagram showing the general or-ganization of the system of this invention;

FIGS. 3A-3C, when placed in order, from left to right, provide a circuit diagram of a portion of the retarder control system of this invention;

FIGS. 4A and 4B illustrate portions of the circuit organization used to determine the reference leaving speeds of cars from the hump and group retarders;

FIGS. 5A and 5B, when placed with FIG. 5B to the right of FIG. 5A, illustrate the circuit organization providing for the determination of the speed at which a car leaves the hump retarder;

FIG. 6 illustrates the electronic counting circuits provided f-or measuring lcar speed at the exit of the hump retarder;

FIG. 7 illustrates graphically how the release speed from the group retarder is selected for each car inaccordance with predetermined characteristics.

To simplify the illustration and facilitate the explana- 'tion of this invention, various parts and circuits .which constitute the emb-odime-nt of this invention are shown diagrammatically and certain conventional illustrations are used. The drawings have been made to make it easy to understand the principles and manner of operation rather than to illustrate the specific construction and arrangement of parts that would be used in practice. The various relays and their contacts are shown in a conventional manner and symbols are used to indicate connections to terminals of batteries and other sources of electric current instead of showing all the Wiring connections to these terminals. Symbols (B+) and (B-) indicate connections to the opposite terminals of a source of voltage suitable for the operation of various electron tubes and the like, and this source of voltage is provided with a tap between the (B+) and (B-) terminals designated by the symbol for a ground connection.

GENERAL SYSTEM FIG. 1 illustratesl a portion of the track layout in a typical car classification yard. A train of cars is pushed up the hump and then the cars are allowed to roll singly or in cuts over the various switches and branch tracks to the final destination tracks. A hump retarder is located ahead of the first switch. Additional retardation is provided by one or more group retarders located in each of the several branch tracks. The gradient of the yard is also shown in FIG. 1 to illustrate that the ca-rs -roll by gravity from the hump to their intended destination tracks.

The block diagram of FIGS. 2A and 2B illustrates hump and group retarders at spaced locations along the track rails. Only one typical group retarder location is shown in this FIG. 2B: the others shown in FIG. 1 are assumed to each have similar apparatus associated therewith. Near the leaving end of the hump retarder and also each group retarder and preferably located between the track rails is a directional antenna which is beamed to transmit a high frequency signal towards approaching cars. The transmitter-receiver 10 associated with the directional antenna 11, for example, provides this high frequency signal and also is responsive to the higher frequency signal that is reflected from approaching cars. lt mixes these two signals of different frequency to obtain a difference or beat frequency which is proportional to car speed. This beat frequency signal is applied to the discriminator 12 which responds to the beat frequency value by selectively controlling the control relays 13. The control relays 13 include speed responsive relays which are actuated at preselected values of the beat frequency corresponding to respective car speeds. They act upon the retarder operating mechanism 14 to effect the proper braking on the car wheels by the brake shoe beams of the car retarder.

In the system of this invention, the hump retarder has associated with it a second directional antenna 15 which directs a rbeam of high frequency energy down the hump towards receding cars. The transmitter-receiver 16 associated with this particular antenna provides an output beat frequency t-hat is proportional to the speed of each car after leaving the hump retarder. At the moment that a car leaves the hump retarder, a control is provided by the control relays over lead 17 to the pulse forming, gating and counting circuits 18. This causes the cycles of the beat frequency to be counted fora preselected interval starting at the time the car leaves the hump retarder. The number o-f beat frequency cycles counted during this iixed interval is a measure of car speed. This car speed information is established as a multi-digit code in the hump leaving speed storage and transfer circuits 19. Although rnore than one car may occupy the stretch of track between the hump and group retarders, the respective code for each car remains identied with that car and is transferred with the car continually as it progresses toward the group retarder. The progress of the car produces `an accompanying code transfer which is affected by va-rious track circuits in the trackway having the associated track relays H-TR and G-TR. The yard automatic switching circuits 3S provide a control, represented by lead 42, that causes the code `to be transferred to the proper group control apparatus according to the preselected route of the car.

Weighing means is provided just ahead of the hump retarder and also just ahead of each group retarder location so that the weight of each car, o-r the weight of the heaviest car in the cut may be determined. The weighing means may comprise a floating weighing -rail such as rail 2() just ahead of the hump retarder which has 'associated therewith a weight detector mechanism 21. The weighing rail selectively actuates contacts of the Weight detector 21 in accordance ywith the extent of its deflection by the weight of a car, and these contacts, in turn, selectively actuate the weight storage relays 22. Weighing means of this kind is shown and. fully described in the pending `application of S. M. Phelps, U.S. Ser. No. 386,- 095 led October 14, 1953. Other types of weighing means may also be provided such as an electronic means comprising a strain gauge.

Other factors being equal, a heavy car passing through a retarder possesses more kinetic energy 4than a light car. Consequently, to slow down a heavy car the retarder must be set to provide a greater braking elfect than is required for a light car. Therefore, contacts of the weight storage relays 22 are used in a circuit organization providing for the control of the retarder operating rnechanism 14 as shown in FIG. 2A so that the retarder can be properly preset for the proper braking pressure in -accordance -with car Weight.

Even when the apparatus associated with .the hump retarder is adjusted to release all cars regardless of Weight from this retarder at the same speed, car Weight information must still be a factor in determining at what car speed the control relays should be actuated in order that the required compensation for the dilferences in performance characteristics of these different classes of cars can be accommodated. For this reason, weight information provided by contacts of the weight storage relays 22 is also supplied to the hump leaving speed circuits 23 so that the computed speed at which the control relays operate can be made different for cars of different -weight classes. This compensation makes it possible for cars of considerably different weights to leave the hump retarder at essentially the same speed when this is desired.

Under certain circumstances, it is desirable that cars be released from the hump retarde-r at different speeds according to car weight. It has been determined experimentally, for example, that light cars tend to be very hard rolling under low temperature conditions. To overcome this effect, it is at times desirable to release light weight cars from the Ihump retarder -at a higher speed. The control provided Iby the weight storage lrelays 22 on the hump leaving speed circuits 23 makes it possible to effect this control.

To provide a more precise control over the braking elfect provided by both the hump and group retarder, each retarder is released in stages rather than at one time. For this reason, the control relays 13 yacting on the retarde-r operating mechanism 14 of the hump retarder, for example, yinclude both a speed relay and an anticipation relay. When the car speed has been reduced by the retarder to a value nearly equal to its intended release speed, the anticipation relay is released, yand this causes the retarder `to open partially from its predetermined closed position. When the car speed is further reduced to the desired release speed, the speed relay is operated, and thisV causes the retarder to then -fbe fully released. In 'this way, the retarder is not required to be operated through its entire range when the car speed has reached its desired value `with `the result that the car speed at the time the retarder becomes fully released can then more nearly equal the computed desired value.

The hump leaving speed circuits 23 at the hump retarder supply voltages to the discriminator 12 lWhose arnplitude is proportional to the desired release speeds for both the speed yand anticipation relays included in the control relays 13. The magnitude of this voltage analog `of speed is influenced by the conditions of the weight storage relays 22 as already described, Iand also by the conditions of the yard speed modifying control 24 and light car modifying control 25. The yard speed manual modifying control 24 is provided so that an operator can vary yover a selected range the speed at which all cars leave the hump retarder. This control is useful as, for example, when a strong head wind is blowing and causing all cars to roll with -reduced speeds between the hump and group retarders with the result that car separation is reduced. Operation of this yard speed manual modifying control 24 to increase slightly the release speeds of all cars from the hump retarder tends to overcome this condition. The light car modifying control 25 is provided to enable the output voltage of the release speed selecting circuit-s 23 to @be increased somewhat for car of the light weight classification.

At each group retarder, the information as to the speed at which a ca-r left the hump retarder is obtained from the hump leaving speed storage and transfer circuits 19 `and .ap-plied over lead 26 t-o the reference entering speed circuits 27. For each value of leaving speed of a car from the hump retarder there is established a particular reference entering speed for that car. This reference entering speed is provided in the form of an equivalent voltage analog whose amplitude represents the expected speed at the entrance to the group retarder for a car with that particular leaving speed from the hump retarder and having easy rolling characteristics.

Since the length of a cut determines to a considerable extent lrow much acceleration it may experience between the hump yand `group retarders, a control is provided from the cut length detector 28 over lead 29 to the reference entering speed circuits 27 so that the voltage corresponding .to reference entering speed may be of the proper value by taking into account this factor of length of cut. This cut length detector 28 is controlled by both the Weight detector 30 associated with the No. 1 -group retarder vand the track relays H-TR and G-TR shown in FIGS. v2A and 2B. For lcuts of two cars and for single cars, when actuation `of weight detector 30 is caused 'by the leading truck, nei-ther the track sections associated with the track relays H-TR and G-TR are then occupied by the cut. The cut is thus detected as being short -by the cut length detector 28. A cut of medium length is able to span simultaneously the weighing rail .associ-ated with weight detector 30 and the track section associated with relay GJFR. This c-ontrols the cut length detector to provide an output on llead 29 indicative of a medium length cut. In a similar way, the simultaneous spanning of the weighing rail and the shunt-ing of the track circuit ass-ociated with relay H-TR causes the cut length detector to provide an output indicating the existence of -a long cut. The `detailed means by which this detection of cut length can be made is disclosed in the lco-pending .application of R. F. Albrighton, Ser. No. 513,321, filed June 6, 1955, now Patent No. 2,814,966. Although the prior application discloses means only for distinguishing between short and 'long cuts, it will be readily clear by analogy from this disclosure how medium length cuts can be detected.

The No. 1 retarder control relays 31 include an exit relay which is actuated when each car or cut leaves the No. 1 retarder. This exit relay is effective over lead 32 to cancel the last stored code in the hump leaving speed storage and transfer circuits 19. This lcancellation makes it possible for codes relating to the hump leaving speeds of following cars to be advanced.

The voltage analog of reference entering speed is provide-d over lead 33 to the modifier 34. The modifier also receives a voltage ove-r lead 35 from the discriminator l36, and this voltage is an anal-og ofthe actual speed of the car -at any instant as it approaches Iand passes through the No. 1 group retarder. The modifier 34 provides a circuit organization for comparing the actual speed of the car at Ia predetermined location With the reference entering speed. The difference in these two values represents the comparative rollability of the car because `a very hard rolling car will, Ifor example, arrive at the group retarder at a speed considerably below the reference entering speed since this is the expected speed of arrival for a car having easy rolling characteristics.

The voltage representing this difference between the voltage analogs of reference entering speed and actual entering speed is multiplied in the modifier 34 by a factor dependent upon the intended route for the car following the Igroup retarder. The information regarding route is applied tothe modifier over lead 37 from the yard automatic switching circuits 38. The multiplying factor can be further affected through operation of the group manual modifying control 38a. This group manual modifying control 38a comprises a manually operated multiposition switch which can be posit-ioned in accordance with track fullness, for example, so that each car can be released from the group retarder with a speed tha-t will cause it to reach coupling speed at any one of various selected zones. exerts a controlling influence over lead 39 to the reference leaving speed circuits 40 f-or this same purpose.

The modifier 34 thus provides a voltage over lead 41 to the No. 1 discriminator 36 which .represents the comparative rollability of each car with this factor being i The group manual modifying lcontrol 38a also portional to car speed to the associated discriminator such as the No. 1 discriminator 36 corresponding to the transmitter-receiver 42.

The reference leaving speed circuits 40 provide voltages to the No. 1 discriminato-r 36 proportional to the car speed at which the speed and anticipation relays of this discrim-inator, respectively, are to be released. The yard automatic switching circuits 38 provide a control over lead 43 to the reference leaving speed circuits 40 so that the reference leaving speed will be selected in accordance with the intended route of the car.

When a car arrives at the group retarder at the reference entering speed, no modification is received from the modifier 34 since the difference between reference entering speed Vand actual entering speed is then zero. Under these conditions, the speed `and anticipation relays of the No. 1 discriminator are then released at car Aspeeds corresponding to the levels selected by the reference leaving speed circuits 4f). However, for cars wh-ich are harder rolling, the speed at entry to the No. l group retarder yis less than the reference entering speed, and the difference between the voltage analogs of these two speeds is effective, after being multiplied by the modifier 34 and applied to the No. l discriminator 36, to raise the values of car speed at which the speed and anticipation relays drop away above the levels preselected by the reference 'leaving speed circuits 40. In this way, the harder rolling cars are allowed to leave the `group retarder at a higher speed to compensate for their harder rolling characteristics.

The reference leaving speed circuits `40 also provide voltages representing the reference leaving speed from the No. 2 -group retarder to the No. 2 discriminator 44 as represented by lead 45. This discriminator 44 also receives the modifying input over lead 46 from the modifier 34 before the car leaves the No. 1 group retarder. Information as to actual car speed is .applied to the No. 2 discriminator 44 on lead 47 by the transmitter-receiver 48 associated wit-h the directional antenna located near the exit end of this No. 2 4group retarder. The No. 2 retarder control relays 49 `are thus controlled in a manner similar to that provided for the No. 1 retarder control relays 31 so that the retarder operating mechanism 50 will cause the partial release of the No. 2 retarder when car speed has been reduced sufficiently to drop away .the anticipation relay .and will ful-ly open the retarder when car speed has been brought to the value effective to drop away the speed relay.

Detailed circuits PULSE FORMING, GATING, AND COUNTING CIRCUITS 1S The pulse forming, gating, and counting circuits 18 of FIG. 2A are shown in the detailed circuits of FIGS. 5A and 5B as including the pulse forming circuits 56, the counter gate circuit 57, the execution pulse -circuit 58, the blnary counting circuits 59, and the speed coding circuits 60. The resulting hump leaving speed information is stored in the speed code storage relays 61.

The pulse forming circuits 56 include means for converting the beat frequency proportional to car speed received and obtained from transmitter-receiver 16 into successive pulses, one for each cycle of the beat frequency signal. This transmitter-receiver 16 is associated with directional antenna 15 facing down the hump so that the beat frequency signal it provides is indicative of the speed of cars receding from the antenna location. Adjacent this location, but pointing in the opposite direction, is another directional antenna 11 which monitors the speed of cars in appro-ach of and passing through the hump retarder. The transmitter-receiver 10 associated with this antenna supplies its beat frequency signal to the hump discriminator 12` which then selectively controls the control relays 13 as previously described. The control relays 13 include an exit repeater relay XP which is picked up when a car is in the hump retarder but drops away as soon as the car leaves the hump retarder. As will be shown,

this dropping away of the relay XP demarcates the beginning of the fixed interval during which the pulses relating to the leaving speed of the car may be applied to the binary counting circuits 59 of FIG. 5B. The detailed circuits for the control of relay XP and the various other relays employed have not been shown; the circuits are the same as those appearing in FIG. 7 of the copending application of H. C. Kendall and J. H. Auer, Jr., Ser. No. 513,364 led June 6, 1955.

The circuit organization shown in FIGS. A and 5B for measuring the leaving speed at the hump retarder may actually be physically remote from the transmitter-receiver 16 since this latter unit would ordinarily be located near its associated directional antenna. Consequently, the beat frequency output signal of the transmitter-receiver 16 is applied over a twisted pair represented by wires 62 and 63 to the input circuit of a cathode follower stage. The clamping stage including tube 65, and the Schmitt amplifier including tribes 66 and v67, comprise a circuit org-anization similar to that disclosed in the previously mentioned copending application Ser. No. 513,364, tiled J-une 6, 1955. These tubes correspond to the tubes 43, 467 47, and 52 shown in FIG. 3A of this prior application, and since the description given therein with respect to these circuits applies equally ywell to the circuits of the present invention, they will not be described in detail here. It is sucient to relate that the cathode follower stage including tube 64 provides the desired high impedance termination to the line wires 62 and 63, and the clamper including tube 65 prevents a large negative bias voltage from being developed at the grid of tube 66 since -this would cause the occurrence of a large amplitude beat frequency signal to mask a following beat frequency signal of low amplitude. The function of the Schmitt amplifier including tubes 66 and 67 is to respond to each cycle of the beat frequency signal by supplying a rectangularly shaped pulse at the plate of tube 67.

The rectangular voltage pulses at the plate of tube 67 are applied to -a differentiating amplifier including tube 68. The control grid of this tube -is connected through resistor 69 to (B+). The cathode is connected to the junction of resistors 70 and 71 connected between (B-) and ground. The plate of this tube is connected through resistor 72 to (B-), and is also connected through resistor 73, resistor 74 and capacitor 75 in parallel, to the plate of tube 76. If it is assumed that tube 76 is non-conductive, then a relatively high voltage will appear ou wire 77. This voltage may be considered as representing the upper voltage level applied to a series potentiometer comprising resistors 74, 73 and 72 with the lower terminal of the potentiometer being connected to (B-). When tube 68 is in a conductive condition, it effectively connects the junction of resistors 72 and 73 through its low resistance plate-cathode circuit to the negative voltage present at the cathode of tube 68 so that, even though a high voltage appears on wire 77, the voltage at the grid of tube 78 is negative sufficiently to cut this cathode follower tube otf. However, for each negative going voltage variation at the plate of tube 67 causing capacitor 79 to discharge and thereby lower the voltage on the grid of tube 68 suflciently below the negative cathode to cause this tube to become nonconductive, the junction of resistors 72 and 73 is effectively disconnected from the cathode of tube 68. The relative value of resistors 72, 73 and 74 is so selected that, under these conditions, viz. tube 68 cut oif and tube 76 cut off so that a high voltage appears on wire 77, the grid of tube 78 will be positive, causing this tube to conduct. The non-conductive condition of -tube 68 persists only for the time required for capacitor 79 to discharge, and since this capacitor has only a small value `0f capacitance, itdischarges very quickly so that tube 68 remains non-conductive for only a brief interval. In this way, however, each negative going voltage variation present in the rectangular pulse output of tube 67 results 10 in the application of a positive going trigger pulse to the grid of cathode follower tube 78, provided only that tube 76 is at that time in a non-conductive state and thereby providing a relatively high voltage on wire 77.

Each positive going trigger pulse at the grid of the cathode follower tube 78 results in an abrupt lincrease in plate current of this tube so that a positive going pulse appears across its cathode resistor 80. Each such pulse is applied over wire 81 and through coupling capacitor 82 and resistor 83 to the starter of the cold cathode tube 84 included in the binary counting circuits 59 of FIG. 5B.

The binary counting circuits 59 comprise seven distinct stages. Only one of the -two cold cathode tubes of each stage is shown in FIG. 5B. These tubes are all normally extinguished and when in this condition may be considered as representing the "0 binary digit; their conductive condition represents the binary digit 1. The binary stages are shown in greater detail in FIG. 6.

The triode tubes 85, 86 and 76 of FIG. 5A are included in a circuit organization which establishes a gating condition of predetermined duration during which output pulses, one for each cycle of the beat frequency, are applied to .the binary counting circuits. The two tubes S7 and 8S provide yan execution pulse after this gating interval to cause the selective picking up of the speed code storage relays 61 which store the information regarding hump leaving speed.

The gating interval for counting pulses relating to the hump leaving speed of a car is initiated by the dropping away of the exit repeater relay XP associated with the hump discriminator 12. In the interests of obtaining the desired accuracy in measurement of hump leaving speed, the predetermined interval during which the beat frequencies are counted is selected to be relatively long, i.e. of the order of one-half second. For a car having a very low speed, relatively few pulses can be counted, however, even during an interval of this length. If the gate is started just subsequent to the occurrences of one of these pulses, a different count may be obtained than if the gate is started just prior to or in coincidence with one of the beat frequency pulses. At low pulse rates, a difference of one count when perhaps only five or so of such pulses will occur within the gating interval represents an error -of appreciable magnitude. For this reason, the gating circuit organization has been devised so that the gating interval will be initiated by the dropping away of relay XP but will actually start only in coincidence with one of the beat frequency pulses occurring at the output of the Schmitt amplifier comprising tubes 66 and 67. As -a result, for a particular beat frequency rate, the same count will always be provided on the binary counting circuits independently of the particular phase relationships between the dropping away of relay XP and the beat frequency pulses.

More specifically, a capacitor 89'is connected through a front contact 90 of relay XP and through resistor 91 to (B+) whenever relay XP is picked up, i.e. whenever there is a car in the hump retarder. Upon the exit of the car from the hump retarder, relay XP drops away so that the then charged capacitor 89 is connected through back contact 90 of relay XP in parallel with resistor 92 and capacitor 93. Some of the charge on capacitor 89 is thereby transferred to capacitor 93.

Tube 85 has its cathode connected directly to (B-), while its control grid is connected through resistor 94 to ground. This results in a grid-cathode voltage for tube 85 to make this tube ordinarily conductive provided that it has the required plate voltage as a result of the charging of capacitor 93. With tube 35 thus conductive, it provides a low resistance through its plate-cathode circuit in parallel with the relatively high resistance of resistor 95 connected from the plate of tube 85 to (B-). Consequently, the plate voltage of this tube is sufficiently below ground and thus below the voltage on the grid of tube 86 that diode 96 is non-conductive.

The square wave of voltage appearing on wire 97 as a result of the beat frequency signal is applied through the differentiating capacitor 98 to the control grid of tube 85. Each positive-going edge of one of these pulses produces a positive trigger pulse on the grid of tube 85, but this pulse can have substantially no affect on the already conducting tube 85. Each negative-going pulse edge, however, produces a negative-trigger pulse on the grid of tube 85, thereby causing the tube to become momentarily non-conductive. The resistance in lthe lower portion of the voltage divider extending from the upper terminal of capacitor 93 and through resistor 99, and resistor 95 in parallel with tube 85 is thereby abruptly increased in value so that a positive-going trigger pulse appears at the plate of tube 85. Since this raises the voltage at the plate of diode 96 appreciably above the negative grid of tube 86, the diode 96 becomes momentarily conductive so that the positive going trigger pulse appears also at the control grid of tube 86.

Tubes 86 and 76 are interconnected to form `a oneshot multivibrator. Tube 76 has its control grid connected through resistor 100 to (B+) so that this tube is normally conductive. The grid of tube 86, on the other hand, -is connected through resistor 101 to (B-) so that it is normally in a non-conductive state. The positivegoing trigger pulse at the grid of this tube 86 causes this tube to be momentarily driven to a conductive state. When this occurs, a regenerative action results which drives tube 76 to a fully non-conductive condition and tube -86 to a fully conductive condition. Tubes 86 and 76 remain in this abnormal state, i.e. with tube 86 fully conductive and tube 76 fully non-conductive, for au interval dependent upon the time required for capacitor 102 to dis-charge. When this occurs, there is an instant reversal of state of these two tubes to their initial conditions.

When this multivibrator is in its normal condition with tube 76 conductive, the voltage at the plate of this tube is at a low value so that the required high positive gating voltage is not present on wire 77. It is only during the interval that the multivibrator is in its abnormal condition with tube 76 non-conductive that the high positive gating voltage appears on wire 77, thereby making it possible for the positive-going Ipulses to appear on wire 81 `and be applied to the binary counting circuits 59 of FIG. B.

For low car speeds which result in a low beat fre quency, there may be a .relatively long time following the dropping away of Irelay XP which charges capacitor 93 before the occurrence of the first negative-going pulse on the grid of tube 85. It is desirable that the time constants of the circuit be such that capacitor 93 will still provide sufcient plate voltage for tube 85 throughout such an interval so that the first negative-going trigger pulse on wire 97 can be effective to produce a positive trigger pulse at the plate of tube 85 and thus trigger the multivibrator. On the other hand, if the charge on capacitor 93 is retained for a long time, it is possible at higher car speeds, lresulting in a higher beat frequency rate to provide another triggering pulse for the multivibrator, after it has restored itself to the normal condition, that would again open the gate and permit trigger pulses to appear on wire 81. This `circuit organization has therefore been so arranged that the first positive trigger pulses at the plate of tube 85 after the dropping away of relay XP will trigger the multivibrator as described and this action will provide a discharge circuit for capacitor 93 having a relatively short time constant so that the multivibrator cannot be triggered again until capacitor 93 has once more been charged as a lresult of a following car passing through the hump retarder.

More specifically, when the multivibrator is triggered by making tube 86 conductive, the normally high plate voltage of this tube which has maintained the cathode of diode 103 so far positive with respect to its plate that this diode isnonconductive is immediately reduced so that the diode can conduct and discharge capacitor 93 through the plate-cathode circuit of tube 86. This quickly reduces the plate Voltage from tube `so that it cannot provide additional positive trigger pulses at this plate which would erroneously affect the operation of the multivibrator circuit.

Throughout the time that the multivibrator is in its abnormal condition, positive trigger pulses appear on wire 81 with a frequency proportional to the speed of the car leaving the hump retarder. At the end of the interval when the multivibrator has restored itself to its normal condition and the counting operation has stopped, it is capacitor 106 in series to the plate of ytube 76. The` negative-going Voltage variation at the plate of tube 76 occurring when the multivibrator restores itself to its normal condition with tube 76 conductive causes tube 87 to become non-conductive for a brief time until capacitor 106 discharges. Throughout the time that tube 87 is non-conductive, a high positive voltage appears at its plate. As soon as the tube again becomes conductive, its plate voltage is abruptly reduced to its normal low va-lue. Tube 88 is operated in a similar manner as a differentiating ampliiier. Thus, each negative-going voltage variation at the plate of tube 87 when this tube is restored to its normal conductive condition causes tube l88 to become noncond'uctive so that a positive-going pulse appears at its plate. The width of this pulse is determined by the time constant for the discharge of the differentiating capacitor 107. Capacitor 108 is connected fr-om the junction of plate resistors 109 and 110 t-o ground. This capacitor prevents the voltage on -bus 111 from rising when tube y88 becomes non-conductive above that normally present at the junction of these two resistors when tube 88 is conductive. If it were not for this capacitor 108, the voltage at the plate of tube 88 would rise substantially to the level of the (B+) source of voltage.

A binary counter having siX stages to provide a 63 count capacity and an extra seventh stage to indicate counts above 63 `during the predetermined gating interval was deemed suicient for determining hump leaving speed. Each stage of the counter may comprise two cold cathode tubes as shown in FIG. 6; only one tube of each pair is shown in the diagrammatic representation of this counter in FIG. 5B. As usual with such binary counters, each stage is actually a scale-of-two pulse divider. The first stage operates between opposite conditions for each input pulse appearing on wire 81` The second stage operates between opposite conditions for each second operation of the rst stage, and so on.

To provide the accuracy of car speed measurement deemed necessary, the length of the gate during which the beat frequency pulses are applied to the binary counting circuits was adjusted so that a speed of 16 miles per hour would result in 64 pulses being counted by the counting circuits. Thus, each one quarter of a mile increment of speed is represented by one additional count on the binary counter. This adjustment of the gate is readily made by simply varying the time required for the multivibrator including tubes 86 and 76 to restore itself to its original state.

In one specific embodiment of this invention, it was considered important to provide detailed speed information only for the range of car speeds between 8 and 16 miles per hour. For car speeds either above or below this range it is then only required that the code representing speed only indicate that the speed is out of this range.

With one count representing a speed increment of ne quarter mile per hour, the range of counts representing speeds from 8 to 16 miles per hour can be represen-ted by five dual-state devices such as the tive relays LS1 to LSS. Actually, the code established in the relays is modified so that one particular permutation of their conditions represents all speeds below 8 miles per hour, and another diierent permutation represents all speeds above 16 miles -per hour.

For car speeds less than 8 miles per hour represented by counts less than 32 the rst tive stages of the binary counter may be in any one of various permutations, but both stages No. 6 and No. 7 are in their 0 conditions. In the diagrammatic representation of this binary counter in FIG. B, the 0 condition of any stage ,is represented by the extinguished condition of the cold cathode tube shown for that stage, while the 1 condition of that stage is represented by the tube being in its conductive stage. For counts less than 32, corresponding to speeds less than 8 miles per hour, tube 116 is, therefore, nonconductive so that there is no voltage drop resulting from current of tube 1Y16 across resistors 117 and 118, and the cathode of this tube is at ground poten-tial. This means that the cathode of diode 119 is also at ground. Because of this, the voltage on wire 120 cannot rise appreciably above ground since this would cause the diode 119 to become conductive and result in a flow of current with a resulting voltage drop across resistors 117 and 118. This means that even though any of the stages 2 to 5 is then in the l condition with its corresponding tube of FIG. 5B conductive, the positive cathode voltage that this tube provides cannot cause the respective Wire 121-4124 to be raised in potential appreciably above ground since none of the plates of the respective diodes 12S-128 can be appreciably raised above the cathode of these tubes which are all maintained at ground voltage. As a result, none o-f the cold cathode tubes 1444147 can then be provided with a positive gating Voltage on its starter.

These circumstances also result in the inability of the control grid of tube 134 to rise appreciably above ground voltage. Since the cathode of tube 134 is positively biased by being connected to the j-unctions of resistors 135 and 136 between (B+) and ground, this tube is, therefore, cut ott so that a high plate voltage is supplied by this tube, through resistor 137, to the control grid of cathode follower tube 138. Although this tube has its grid connected through resistor 139 to (B-), the high plate voltage obtained at such time from the plate of tube 134 overcomes this bias so that cathode follower tube conducts a substantial plate-cathode current. Even though this tube has its cathode connected through resistor 140 to (B-), the large plate current flow results `in a positive cathode voltage. This positive cathode voltage is applied over wire 141 to the plate of diode 142 so that this diode becomes conductive and a positive gating voltage then is applied to the starter of cold cathode tube 143 through resistors 14451 and 145a. As a result, for a count in the binary counter of less than 32, the cold cathode tube 143 has its starter positively biased and at the same time the starters of the remaining tubes 144-147 are prevented from receiving such positive bias voltage. This means that the execution pulse appearing on wire 11:1 at the conclusion of the gating interval can result in the ring of only the cold cathode tube 143, since only the starter of this tube will then, as a result of its positive bias voltage, be sufficiently raised above the cathode to re the tube. When this tube is tired, current passes from (B+), through the plate-cathode circuit of tube 1413, and the winding of relay LS1, to ground so that the relay is picked up.

For a count of 32 in the binary counter circuits, the cold cathode tube 116 of stage No. 6 is fired but all other counting tubes are extinguished. The tiring of this tube causes its cathode potential to rise so that the voltage on -the anode of diode 119 is no longer prevented from rising substantially above ground potential. However, since none of the other tubes for the other stages are conductive for this count of 32, none of the diodes 12S-128 has its plate voltage raised so as to make possible a rise in potential on wire 120. Consequently, tube 134 remains cut off with the result that a positive cathode voltage is again provided by tube 138 on wire 141. The starter of cold cathode tube 143 receives a positive bias in the same manner as for codes less than 32 so that only this tube will be tired in response to the execution pulse.

For a count `of 33 in the binary counter circuits, tube 116 of the No. 6 stage is still conductive, and tube 84 of the No. 1 stage is now also conductive. Again none of the diodes 12S-128 can become conductive since none of the cold cathode tubes 150-153 is conductive. Tube 134 again remains non-conductive so that a positive voltage appears on the plate of diode 142 and thereby provides the positive biasing voltage on the starter of cold cathode tube 143. At this time, the cold cathode tube of the No. 1 stage also provides positive biasing voltage through resistor 154 and resistors 144a and 145a to the starter of cold cathode tube 143. Therefore, for a count of 33 in the counting circuits, only cold cathode tube 143 can be tired by the execution pulse.

For any of the counts 34 to 63 inclusive, one or lmore of the cold cathode tubes of stages Nos. 2 to 5 are fired,

lthe tube of stage No. 6 is tired, and Ithe tube of stage No. 7 remains extinguished. Whichever tube is red then provides a positive cathode voltage to the plate of the respective diode 12S-128 so that wire 120 is raised in potential. With Ithe cathode of tube 116 also raised at this time, the voltage on wire is not clamped to a near zero voltage but can rise above ground and overcome the cutoff bias on tube 134 so that this tube will conduct. When this occurs, the plate voltage of tube 134 is substantially reduced so that the cathode follower tube 138 has its grid voltage lowered with a resulting marked decrease of its output cathode voltage. This so lowers the voltage on the plate of diode 142 that the required bias cannot be provided for the ystarter of cold cathode tube 143. Under such conditions, each of the cold cathode tubes 143447 has its starter positively biased only if the respective cold cathode tube in the counting circuits is conductive. For example, if tube of stage No. 2 is conductive, the positive voltage present at the junction of its cathode resistors 155 and 156 is then applied through resistor 157 and resistors 158 and 159 to the starter of cold cathode tube 144. After the counting operation has ceased, the execution pulse appears on bus 111. This positive pulse, when added to the positive bias voltage already present on :the starter, sufliciently raises the starter voltage with respect to the grounded cathode to cause the :tube to re. This results in the picking up of relay LSZ in a manner already described.

For all counts above 63, tube 160 of the No. 7 stage is tired. Since detailed speed information is not required lfor such high speeds, only one permutation of the relay conditions is utilized for indicating all counts of 64 and above. This is accomplished by supplying the positive cathode voltage of tube 160, when this tube is conductive, over bus 161 to the plates of the diodes 162-166. This results in a positive voltage being applied tothe starters of all the cold cathode tubes 143-147 regardless of Whether the cold cathode counting tube of the respective stage is then fired or not. All the cold cathode relay control tubes then have the positive biasing voltage so rthat the execution pulse causes all of these tubes to be tired. The relays LS1 to LSS then are all picked up under these circumstances.

The cold cathode tubes used in the binary counting circuits and also for the relay control tubes all tend to remain conductive when once controlled to such condition unless extinguished by reducing theplate-cathode voltage `for a long enough time to cause the glow to be extinguished. After the code relative to car speed information has been transferred to the relays LS1 to LSS, the counting circuits must be restored to their initial condition so that they can properly count pulses relative to the next car leaving the hump retarder. In order to clear out the counting circuits, the positive voltage applied to the plates of all the cold cathode tubes is actually btained through a circuit which includes a back contact 167 of the track lrelay H-TR as shown in FIG. 5A. The front truck of each car enters the track section and results in the dropping away of relay H-TR so that the back contact 167 of this relay will close and permit positive voltage to be applied through this contact from (B+) to al1 the cold cathode tubes shown in FIG. 5B. This action occurs prior to the dropping away of the exit repeater relay XP which is the signal for the initiation of ythe counting operation. When the last truck of a car or cut moves out o-f the track circuit associated with track relay H-TR, this .track relay is picked up and its back contact 167 opens so that all positive voltage is removed from the counting tubes and they are then immediately extinguished.

Each speed code stored in the relays LS1 to LSS is transferred through other speed storage relays to the reference entering speed circuits of the group retarder apparatus by means diagrammatically represented by block 19 of FIG. 2A. The rectier connected in parallel with each of the relays LS1 to LSS, such as rectifier 168 associated with relay LS1, prevents an erroneous second picking up of these relays in response :to the same code in the binary counting circuits in the event that there is an intermittent closure of the back contact 167 of relay H-TR. More specifically, when this back contact 167 rst opens, each of the cold cathode tubes 143- 147 then tired is extinguished. The deenergization of the respective relay produces an induced voltage in the winding of that relay that momentarily makes the cathode substantially negative with respect to ground. If the back contact 167 of relay H-TR were then to momentarily reclose because of `some erratic operation, positive energy would again be applied to the plates of all the tubes 143-147 and any tube then having its cathode momentarily below ground might readily again be red because it would then have the required positive startercathode voltage. Such a condition is prevented by the rectifier 168 which is so poled that it will become conductive upon any tendency of the cathode of tube 143 to become negative.

One form that the cold cathode binary counting circuits of FIG. 5B may assume in actual practice is shown in FIG. 6. Each of the various counting stages comprises two cold cathode tubes. Between each successive pair of stages is a pulse forming stage including a single cold cathode tube.

Initially all the cold cathode tubes of the binary counters are non-conductive. The first positive-going trigger pulse on the wire 81 is applied through coupling capacitors 82 and 333 and through the respective resistors 83 and 171 to the starters of the two tubes 84 and 170 of the rst stage. Tube 170 has its starter connected through resistors 171 and 172 to the junction of resistors 173 and 174 in the cathode circuit of tube 84. Since tube 84 is non-conductive at this time, the starter of tube 170 does not receive the required positive biasing voltage so that this tube cannot be tired by the positive trigger pulse of limited amplitude that is applied from wire 81 to its starter. On the other hand, the starter of tube 84 is connected through resistor 83 to the junction of the voltage dividing resistors 175 and 176 connected between (B+) vand ground. The starter of this tube thereby receives a positive biasing potential at all times so that it can readily be tired by this first trigger pulse appearing on wire 81.

After tube S4 has been tired by the iirstinput trigger, the starter of tube receives a positive biasing voltage from the cathode circuit of tube 84 so that it will be tired by the second trigger pulse on wire 81. When this occurs, there is an increased voltage drop momentarily across the common plate resistor 177 for these tubes. At this instant of firing of tube 170 the capacitor 179 associated with this tube has not yet been charged so that the plate voltage can readily be reduced. The cathode of tube 84 is relatively high at this time, however, and is maintained at this level by the charged capacitor 178 so that the decrease of plate voltage on both tubes 170 and 84 cannot be accompanied by any decrease of cathode voltage of tube 84. The plate-cathode voltage of tube 84 therefore drops momentarily below the required sustaining value so that this tube is extinguished.

The next or third positive trigger pulse on wire 81 will again re tube 84 in the manner described. These two tubes 84 and 170 are thus alternately tired in response to successive pulses on wire 81.

The tube 180 in the pulse forming stage No. 1 is actually a repeater of tube 170 in the No. 1 counting stage in the sense that its starter also receives the required positive biasing voltage from the cathode circuit of tube 84. Therefore, this tube is red for each second input pulse that also results in the tiring of tube 170.

The plate circuit of tube 180 includes resistors 181 and 182 with their junction connected through capacitor 183 to ground. The cathode circuit includes resistors 184 and with their junction connected through a similar capacitor 186 to ground. Capacitors 183 and 186 are preferably of the same value of capacitance. Similarly, resistors 181 `and 185 are selected to have the same value of resistance as are also the resistors 182 and 184. The resistance of the two equal resistors 185 and 181 is generally consider-ably larger than that of the two resistors 184 and 182. The total series resistance in the cathode circuit equals the total plate circuit resistance.

At the instant tube 180 is tired, the voltage drop in plate and cathode circuits is equal because of the equal resistance of these circuits so that the voltage on wire 187 rises abruptly from ground to a value which is onehalf of the value of the (B+) voltage supply less the substantially fixed voltage drop between plate and cathode of tube 180. Immediately after tube 180 is tired, capacitor 186 begins to charge and the initially charged capacitor 183 begins to discharge. Since the time constants for the charge and discharge of these capacitors is equal, the voltage at the junction of cathode resistors 184 and 185 rises at the same rate that the voltage at the junction of plate resistors 181 and 182 decreases. At all times, however, the voltage at the cathode of tube 180, which is midway in resistance between these two points, remains at the same level with the result that the voltage pulse on wire 187 has a at-topped characteristic. This condition persists until the effective resistance inthe platecathode circuit becomes so high as a result of the charging of capacitor 186 and the discharging of capacitor 183 that conduction can no longer be sustained and the tube is then extinguished. This results principally because of the very high resistance of resistors 181 and 185. At such time, the voltage at the cathode of tube 180 decreasesv exponentially to ground. The result is, therefore, that each second input pulse on wire 81 causes the iiring of tube 170 and also of tube 180 yso that a positive, attopped trigger pulse appears on wire 187. Each such pulse on wire 187 is effective to alternately re the two tubes 150 and 188 of the next counting stage in the same manner as described in connection with the rst counting stage.

Each counting stage of the binary counter circuits thus operates as a scale-of-two pulse divider with the interposed pulse forming stages providing the required pulse operations of the preceding stage.

The last two stages of the binary counter circuits are modified in that they include only a single gas discharge tube rather than two and also in that there is no pulse forming stage between these two counting stages. This comes `about because of there not being any need for detailed speed information when the count in the counter is greater than 64. In a count of 64, it is necessary that stage No. 7 be operated Afrom its normal condition and this establishes the distinctive code resulting in all of the speed relays being energized as previously described. Since the condition of the preceding stages is then irrelevant, it is not necessary to `restore stage No. 6 to its original condition so that no second tube is required for the stage No. 6 to restore the first tube to its non-conductive position. For all counts in excess of 32, tube 116 is conductive and provides from its cathode circuit the required positive bias for the starter of tube 160 of stage No. 7. At the count of 64, therefore, a positivegoing trigger pulse appears on wire 189 which is applied through capacitor 190 and resistor 191 to the starter of tube 160 to make this tube conductive. Both tubes 116 and 160 thus remain conductive for all counts in excess of 64 and they are restored to their normal non-conductive conditions only when the car or cut leaves the track section so that track relay H-TR is picked up in the manner previously described in connection with FIG. B.

DISCRIMINATORS Each transmitter-receiver provided for the speed monitoring equipment of a retarder has associated with it a discriminator. The double group retarder of FIG. 3B is shown as having a directional antenna near the eXit end of each retarder. The transmitter-receiver 42 associated with the first of these directional antennas supplies its beat frequency output to the No. 1 discriminator 36. The No. 2 retarder similarly has a transmitter-receiver 43 associated therewith which provides its output beat frequency to a No. 2 discriminator 44.

It is a function of each discriminator to control a speed relay such as relay S1 and an anticipation relay such as relay A1 (see No. 1 discriminator 36) when the speed of a car as determined by the frequency of the beat frequency signal from the associated transmitter-receiver reaches a particular value. As car speed is reduced toward the desired value, the anticipation relay A1 is first released and this causes the partial release of the retarder braking mechanism. When car speed is actually reduced to the desired release speed, the speed relay S1 is releasedA and then the retarder is operated to its fully open condition.

Each discriminator shown in FIGS. 3B and 3C is smilar to that disclosed in detail in the prior copending application Ser. No. 513,364, filed June 6, 1955 so that a Adetailed description of the electronic circuits of each discriminator is not deemed to be essential here. With reference to the block diagram of FIG. 3B, the beat frequency signal provided by the transmitter-receiver 42 is indicated as being applied over wire 195 to a cathode follower 196. The output of this cathode follower is then applied as an input signal to the modifier 34. The signal is also applied to the pulse forming circuits 197, the check relay control circuit 198, and the exit relay control circuit 199. The exit relay control circuit 199 controls the relay IEX in accordance with the amplitude of the beat frequency signal. This circuit organization causes relay LEX to be picked up whenever the beat frequency signal has an amplitude above some predetermined minimum value and to release when this signal reaches a low value indicating that the car or cut has passed over the directional antenna and is at the point of leaving the respective retarder. The check relay control circuit 198 also operates in accordance with beat frequency signal amplitude but is instead so organized that it causes the picking up of relay lCK when the weight detector is first actuated provided the beat frequency signal has an amplitude above some low minimum Value with the result that this relay is actually picked up just Iprior to the entry of a car or cut into the associated retarder and remains picked up while the car is in the retarder.

The pulse forming circuits 197 respond to the beat frequency signals by providing an output comprising a square wave of voltage whose frequency equals the frequency of the original beat frequency signal. This square wave of voltage is amplified by the amplifier 200 and applied to both the speed relay control circuit 201 and the anticipation relay control circuit 202.

Various relationships between speed, frequency, and voltage may be established. As an aid in describing the operation of this system, it is desirable to assume certain relationships among the different quantities, In one specific embodiment of this invention, the high frequency signal that was transmitted towards moving vehicles was selected to be of a value which would result in a beat frequency of approximately 7.5 cycles per second for each mile per Ihour of car speed. A car moving at 8 miles per hour, for example, then causes a beat frequency signal of 60 cycles per second. Furthermore, the relationship between frequency and voltage was established on a one-to-one basis. Thus, the voltage analog relating to a car speed of 8 miles per hour with a resulting beat frequency of 60 cycles per second was a D C. voltage of 60 volts.

The speed and anticipation relay control circuits 201 and 202, respectively, of FIG. 3B are each shown as receiving an input over Wire 205 from the modifier 34 (see FIG. 3C). If the voltage that the modifier provides is assumed for the moment to be at zero or ground level, then the speed relay control circuit 201 operates in such a manner that it will cause relay S1 to drop away when the frequency of its square wave input on Wire 203 equals, in cycles per second, the value in volts of the control voltage then appearing on wire 204. This voltage appearing on wire 204 is precomputed, in accordance with various factors, to correspond to the desired leaving speed of a car from the retarder, without taking into account any effect that the modifier may have in accordance with its determination of car rollability. This is known as the reference leaving speed. The modifier is able, by the voltage `it supplies on wire 205, to raise the car speed at which actuation of the speed and anticipation relays occurs. It does this in accordance with the amount by which the speed at entry to the group retarder departs from the norm which is, according to the present invention, the entry speed, i.e. reference entering speed, that a car of good rolling characteristics will have. A car reaching the group retarder with this precomputed reference entering speed will then not require any modification by the modifier 34 and its release speed will then be the reference leaving speed in accordance with the control voltage appearing on wire 204.

From this description, it follows that the preselected voltage appearing on wire 204 represents the Voltage analog of the desired release speed for a car having good rolling characteristics and thus arriving at the group retarder at the reference entering speed so that it requires no modification. The effect of the modifier is merely to add to this precomputed release speed in accordance with the performance of the car over the stretch of track between hump and group retarders.

The discriminator 12 associated with the hump retarder (see FIG. 2A) is similar to the No. 1 discriminator 36 just described. The only difference is that no modifying input in accordance with car rollability is then applied to the speed and anticipation relay control circuits. Therefore, the corresponding wire 205 is connected directly to ground with the result that the speed and anticipation relays which effect control of the hump retarder are actuated entirely in accordance with the control voltages obtained from the hump leaving speed circuits 23.

HUMP LEAVING AND REFERENCE LEAVING SPEED CIRCUITS The hump leaving speed and reference leaving speed circuits of FIGS. 4A and 4B include sources of voltage,

potentiometers, resistors, and circuit selecting contacts of a plurality of relays. In each case, the circuits provide an output voltage for the anticipation relay control circuit of an associated discriminator that is proportional to the desired car speed at which this relay should release and thereby partially open the retarder. Another output voltage is provided for the speed relay control circuit and is similarly proportional to the slightly lower car speed at which this relay should release and fully open the retarder. For the group retarders, the relay control circuits are further subject to a modifying control from the modifier 34 as described which provides an additional factor varying the release speed previously determined in accordance with car performance.

Even though all cars may, under some circumstances, be desired to leave the hump retarder at the same speed, the release speed selecting circuits must take into account car weight so that both speed and anticipation relays for the hump discriminator will be actuated at slightly different car speeds for different weight classifications. This is done to compensate for the different amounts of acceleration that cars of different weights experience during the short interval between dropping away of the speed relay and the actual releasing of the retarder mechanism as has been explained. For this reason, the hump leaving speed circuits 23 for the hump retarder shown in FIG. 4A comprise circuit selecting means controlled by the weight storage relays 22. These relays are selectively actuated by the weight detector 21 of FIG. 2A. This control provided by the weight storage relays is diagrammatically,illustrated for convenience in FIG. 4A by a three-position switch Whose rotary contact 210 may be operated to any .one of three different positions, H,

M, or L designating cars of heavy, medium, and light weight classifications, respectively.

The hump leaving speed circuits for the hump retarder shown in FIG. 4A are substantially the same as those appearing in FIG. 5A of the prior mentioned application U.S. Ser. No. 513,364. When the contact 210 is in its center position for a car of medium weight classification, the voltage appearing on wire 211 is the same as that appearing on the tap of potentiometer 212 so that when the beat frequency signal has been reduced in frequency to a value equal to the level of this voltage in volts, the speed relay controlled by the associated hump discriminator will be released.

An independent voltage supply designated by the battery 213 is provided so that with the contact 210 in its H position, the control voltage on wire 211 will be of a somewhat lower value determined by the position of the tap on potentiometer 214. For cars of lightweight, the relay S control voltage is similarly increased somewhat above that provided for cars of medium weight classification. The relay A control voltage appearing on wire 215 is, for each weight classification, at a somewhat higher amplitude than appears on wire 211 for the control of the speed relay S to thereby cause the discriminator to always cause the release of the anticipation relay at a somewhat higher car speed.

One distinction over the circuits disclosed in the prior mentioned copending application is in the provision of a light car modifying control represented by switch contact 216 which is effective to pick up a relay WSP when operated to its right-hand position. When this is done, wire 217 is no longer connected through b-ack contact 21S of relay WSP to the movable tap of potentiometer 219 but is now connected instead through front contact 218 of this relay to the movable tap of potentiometer 220. .The reason for providing this control is that it has been found under certain weather conditions, particularly when low temperatures are prevailing, that cars of light weight tend to become very hard rolling. As a result, these cars do not achieve the necessary separation between hump and group retarders, and, to overcome this, it is necessary that they be released from the hump retarder at a higher speed. Thus, by operating the switch 216 to the righthand position a somewhat higher voltage appears on both wires 211 and 215 as a result of the adjustment of the t-ap on potentiometer 220 as compared to that on potentiometer 219.

The yard speed manual modifying control comprises a three-position switch 221 which is effective to raise or lower the hump release speeds of all cars regardless of weight. In the (-l-) position, wire 222 is connected to ground through the entire resistance of potentiometer 223 and that portion of potentiometer 224 to its tap. This provides a greater resis-tance between wire 222 and ground, thereby raising the voltage on both wires 211 and 215. In a similar Way, operating switch to its position reduces the voltage on wires 211 and 215 to cause a lower release speed for all oars from the hump retarder.

The reference leaving speed selecting circuits provided for the group retarders and shown in FIG. 4B are very similar to those just described for the hump retarder. One exception is that the basic voltage divider includes a selected one of a plurality of variable resistors. These are selected by the automatic switching circuits in accordance with the route to be taken by a particular c-ar. This effect of the automatic switching circuits is diagrammatically illustrated by a multi-position switch contact 225 which can be moved to any one of a number of different positions dependent upon the route to be taken by the car through the classification yard. The variable resistance corre-sponding to each route is adjusted according to conditions over that route. For a route having considerable curvature or other factors tending to provide extra rolling resistance, the variable resistance is adjusted to provide a relatively large amount of resistance. This has the effect of increasing the resistance between ground and the movable tap of potentiometer 226 with the result that the control voltages for both the speed and anticipation relays of the respective group retarder are increased. The reference leaving speed of each car from the group retarder is thus varied as required to compensate for the particular characteristics of the rou-te it will take. For a double group retarder location, the automatic switching circuits comprise means for transferring route information with each car so that it can be effective on the release speed selecting circuits for the respective retarders of the group successively.

An electromagnetic relay FP-0 with its associated contacts 227 and 228 is also shown in connection with the release speed selecting circuits for the retarder. The reason for activating this relay Iand thereby affecting the predetermined release speed for a car will subsequently be described in detail. When this relay is picked up, its front contact closes to shunt all the variable resistors 229. This has the effect of making the control voltages for the speed and anticipation relays independent of car route. The simultaneous opening of back contact 228 inserts additional resistance in the voltage dividing network dependent upon the adjustment of potentiometer 230. Therefore, upon actuation of relay FP-(l, the relay control voltages assume values which are affected according to car weight but are independent of car route, and the level of these voltages can be varied as desired by adjustment of potentiometer 230.

As with the hump leaving speed circuits shown in FIG. 4A, those for the group retarders also are shown as having a multiposition switch having the ganged rotary contactors 231 and 232 selectively operated in accordance with car weight. Until the weight detector is actuated by a car, the weight storage relays have no weight information stored therein so that it may be considered that the rotary contactors 231 and 232 are not in any of the H, M, or L positions. It is desirable, however, that control 21 voltages appear at such time on both Wires 233 and 234 in order that the relay control circuits in the corresponding discriminator will be operating at -about their proper range of operation so that when a car does approach there will be a minimum delay before the relay control circuits are being properly controlled and effective to release the speed and anticipation relays at the predetermined car speeds. Therefore, the condition of the weight storage relays when no car weight information is stored therein is designated by a position O of the rotary contactors 231 and 232. This makes it possible for the voltage on the movable tap of potentiometer 226 to be applied over wire 235, rotary contact 231, wire 236, to the Wire 233, 4and also over rotary contact 232 in the O position, to wire 234. The speed and anticipation relay control circuits thus both receive the voltage level that is the voltage analog of the desired leaving Ispeed for a car of medium weight classification since it is this same voltage that will normally appear on wire 233 when rotary contact 231 is in its M position.

REFERENCE ENTERING SPEED CIRCUITS The information relative to the `speed at which a car leaves the hump retarder is stored in the relays LS1-LS5 which are shown in FIG. 5B and also in FIG. 3A. This speed information is transferred with each car or cut as it rolls from the hump to the group retarders. The routing of the information to the proper group retarder location can be determined in accordance with the conditions of the automatic switching circuits, and the time of transfer of information is readily obtained from the actuations of the track relays associated with the various track circuits in the route between hump and group retarders. The result, therefore, is that the multi-digit code representing leaving speed from the hump retarder is eventually stored in the relays SIP-SSP.

The function of the reference entering speed circuits is to provide a voltage which will be the voltage analog of the expected speed of arrival at the group retarder for a car whose leaving speed from the hump retarder is known and whose rolling characteristics are assumed to be those of a car that is easy rolling. To provide this direct voltage, a voltage divider comprising the three series potentiometers 240, 241, and 242 connected between (B+) and ground is provided. The variable taps of the two potentiometers 240 and 241 are connected together through a resistor 243 having a number of individual taps. The wire 245 on which the voltage analog of reference entering speed is to appear is selectively connected to these taps in accordance with the conditions of the relays SIP-SSP. To simplify the drawings, the control provided by these relays is diagrammatically illustrated by a multi-position rotary contactor 244. The overall effect is that wire 245 is connected to a selected one of these taps entirely in accordance with the speed at which a car leaves the hump retarder The voltage at the upper terminal of resistor 243 is selected in accordance with the adjustment of potentiometer 240; similarly, the voltage at the lower terminal of resistor 243 is dependent upon the adjustment of the variable tap on the other potentiometer 241. The voltage on wire 245 is therefore variable between these two limits with the exact value depending upon the position of contactor 244. The taps on the resistor 243 need not necessarily be uniformly spaced, but may be placed as Vrequired in order to provide exactly the desired voltage level on wire 245 in accordance with the code of hump leaving speed stored in relays SIP-SSP.

A cut length detector 28, whose general organization has already been described, is shown in block diagram form in FIG. 3A. When a single car or, perhaps, a cut of two cars is in approach of the No. 1 group retarder, both the relays 2TPS and 2TPS-A `are energized. For a cut of medium length, relay 2TPS is maintained in its dropped away condition during the time that the cut is in approach of and passing through the group retarders.

22 For a long cut, both the relays 2TPS and 2TPS-A remain dropped away. The cut length detector 28, therefore, gives an indication through the conditions of these two relays as to whether a cut is short (one or two cars), of medium length, or is a long cut.

The relays SIP-SSP shown in FIG. 3A control through their contacts the selective energization of relay D. According to the description already given, all these storage relays for hump leaving speed are dropped away to represent hump leaving speeds which are below some minimum value. The condition wherein all these relays are picked up, represents another special condition indicating that hump leaving speed is above some predetermined maximum value. Since both these extreme conditions are out of the range of measurement of the system, it is desired that some compromise voltage be supplied to the modier to represent an arbitrary difference between reference entering speed and actual entering speed rather than have this level determined in the usual manner by cornparing reference entering speed with actual entering speed. Therefore, two alternate circuits are provided for the energization of relay D. One of these includes all of the front contacts 246-250 in series and the other all of the back contacts 252-255 in series. Therefore, when either all (speed to high) or none (representing no code) of the relays SIP-SSP is picked up, or relay SIP up and S2PS5P down (speed too low) relay D has its Winding energized and is picked up. This picking up of relay D results in the substitution of a compromise voltage level again representing an arbitrary difference between reference entering speed and actual entering speed. More specically, the reference entering speed appearing on wire 245 is applied to the cathode of tube 256 included in the clamper 257 of modifier 34. The output of this clamper is applied to the cathode follower 258 whose output 4appears on wire 259. Under normal conditions, with relay D dropped away and relay 2TPS-A picked up indicating that there is a short or 4medium cut in approach of the group retarder, this voltage on wire 259 is applied through back contact 261 and thus to the D.C. amplifier 263. However, when relay D is picked up wire 262 is connected through front contact 261 of this relay D to a tap on potentiometer 264. Potentiometer 264 is adjusted to provide a voltage on wire 262 representing a suitable compromise value representing an arbitrary difference between reference entering speed and actual entering speed.

If relay 2TPS-A is dropped away for a long cut in approach of the group retarder relay D is again energized through back contact 260 of relay 2TPS-A. Then wire 262 is again connected through front contact 261 to the tap on potentiometer 264. For a cut of medium length, relay 2TPSA is picked up by the cut length detector when there is a car in approach of the No. l group retarder but relay 2TPS remains dropped away. Therefore, back contact 266 of this relay remains closed to shunt thereby the portion of the potentiometer 242 between its tap and ground. This has the effect of lowering the voltage on wire 245, thereby providing automatically a lower reference entering speed voltage for cuts of medium length which have less distance between hump `and group retarders over which they can accelerate, and, therefore, with other factors being equal, arrive at the group retarder with a lower speed than do short cuts.

MODIFIER The modier receives over wire 245, a voltage level that represents the expected speed of arrival at the group retarder for a car having good rolling characteristics and taking into account the speed at which it left the hump retarder. At the same time, the modifier receives a beat frequency signal over wire 265 that is indicative of the actual speed of the car. At the instant that the check relay lCK associated with the No. l discriminator is picked up on the approach of a car, a comparison is made between the predetermined reference entering speed and 

